A blow-molding device generally comprises a structure and a platform mounted to rotate on the structure about an axis of rotation. The platform is provided on its periphery with blower members and with molds mounted under the blower members. The device also includes control means for moving the molds between an open state and a closed state, a transporter for loading preforms into each of the molds, and a transporter for removing containers that have been blow-molded on the platform. Loading, blow-molding, and removal are performed in zones of the platform through which each mold passes in succession during the rotation of the platform. By way of example, the transporters comprise transfer stars and/or rectilinear transporters.
There exist molds that are constituted by two movable portions that are hinged to each other to move between a mold-open position and a mold-closed position. The mold is held in the closed position by means of a locking pin that is of dimensions suitable for co-operating with the hinge pin between the mold portions to withstand the blow-molding forces.
There also exist molds that comprise a stationary portion with a movable portion that is hinged thereto. The control means for moving the movable portion between the closed and open positions comprise two links connected to each other to form a toggle that also serves to hold the movable portion in its closed position.
Blow-molding is performed at a pressure of several tens of bars, conventionally forty bars, thereby giving rise to large forces on the molds, the hinges, and the mechanisms for holding the molds in the closed state. The molds and their holding mechanisms thus comprise parts that are bulky in order to withstand such forces. Nevertheless, the forces contribute to premature wear of the hinges of the movable portions of the molds and of the holding mechanisms, which wear makes it necessary to provide devices for taking up slack. The overall amount of wear is increased by the means for holding the mold in the closed position being complex and having a large number of hinges.
The complexity of the holding means therefore has an influence on maintenance costs and also contributes to the overall size and weight of the platform, thereby increasing its inertia.